Automotive drive axles can include an axle housing, a pair of axle shafts, an input pinion assembly, and a differential assembly that can include a differential housing, a ring gear mounted to the differential housing and a differential gear set disposed within the differential housing. The axle shafts can be received in and rotatably supported by the axle housing for rotation about a first axis. The input pinion assembly can be received in and rotably supported by the axle housing for rotation about a second axis. The pinion assembly can be meshingly engaged with the ring gear. Accordingly, the ring gear and input pinion assembly can be arranged with a hypoid gear configuration. Alternatively, the ring gear and pinion may be of any other conventional type. The differential housing can be rotatably mounted to the axle housing via a pair of roller bearings for rotation about the first axis. The differential gear set can include a pair of side gears, each coupled for rotation with a respective one of the axle shafts, and a plurality of mating differential pinion gears. The side gears can be rotatably supported within the differential housing. The pinion gears can be coupled to and rotatably supported by the differential housing. The pinion gears can be meshingly engaged with the side gears such that rotation of the differential housing causes corresponding rotation of the bevel side gears. Accordingly, the side gears and pinion gears can be arranged in a bevel gear configuration. In this manner, an automotive drive axle can be configured to transmit rotary power supplied to the pinion assembly through the differential assembly to the axle shafts in a predetermined manner.
Providing adequate lubrication to the components of an automotive drive axle is important to the operation and longevity of the automotive drive axle. For example, it is important to properly lubricate the various gears and pinions of the automotive axle assembly including their teeth and the bearing surfaces on which they are supported for rotation. Many automotive axle assemblies utilize splash lubrication to lubricate the various gears and pinions wherein a rotating component, such as the ring gear and/or the differential housing rotates through a liquid lubricant that is disposed in a sump that is defined by the axle housing. Lubricant clings the to the rotating component as it passes through the lubricant in the sump and is thereafter slung outwardly from the rotating component due to centrifugal force.
Among the drawbacks of splash lubrication is the loss in operating efficiency associated with the churning of the lubricant that occurs to lubricate the components in the manner previously described. With increasing emphasis on vehicle fuel economy, improvements in the operating efficiency of automotive axle assemblies are becoming increasingly important. One approach to achieving improvements in operating efficiency that we have considered is to reduce the quantity of lubricant in the sump of the axle housing to lower the level of the liquid lubricant stored therein. Lowering the lubricant level reduces the rotational spin loss that occurs when the rotating component passes through the liquid lubricant in the sump. A reduction in the quantity of liquid lubricant also offers other benefits, including material cost savings and reduced life-cycle pollution. However, reduced quantity of liquid lubricant may not provide adequate lubrication where the axle assembly relies solely on conventional splash lubrication techniques.